Related subject matter is disclosed in a commonly-owned, co-pending patent application entitled xe2x80x9cAPPARATUS AND METHOD FOR QUALIFYING A POLISHING PAD IN A CHEMICAL MECHANICAL PLANARIZATION SYSTEMxe2x80x9d Attorney Docket No. 7103/181, filed on even date herewith.
The present invention relates to an apparatus and method for conditioning a chemical mechanical planarization process. More particularly, the present invention relates to an apparatus and method for conditioning a fixed abrasive polishing pad used in the chemical mechanical planarization of semiconductor wafers.
Semiconductor wafers are typically fabricated with multiple copies of a desired integrated circuit design that will later be separated and made into individual chips. A common technique for forming the circuitry on a semiconductor is photolithography. Part of the photolithography process requires that a special camera focus on the wafer to project an image of the circuit on the wafer. The ability of the camera to focus on the surface of the wafer is often adversely affected by unevenness in the wafer surface. This sensitivity is accentuated with the current drive toward smaller, more highly integrated circuit designs. Semiconductor devices are also commonly constructed in layers, where a portion of a circuit is created on a first level and conductive vias are made to connect up to the next level of the circuit. After each layer of the circuit is etched on a semiconductor wafer, an oxide layer is put down allowing the vias to pass through but covering the rest of the previous circuit level. Each layer of the circuit can create or add unevenness to the wafer that is preferably smoothed out before generating the next circuit layer.
Chemical mechanical planarization (CMP) techniques are used to planarize the raw wafer and each layer of material added thereafter. Available CMP systems, commonly called wafer polishers, often use a rotating wafer holder that brings the wafer into contact with a polishing pad moving in the plane of the wafer surface to be planarized. In some CMP systems, a fixed abrasive polishing pad is used to polish the wafer. The wafer holder then presses the wafer against the rotating fixed abrasive polishing pad and is rotated to polish and planarize the wafer.
CMP systems using a fixed abrasive pads require the presence of features on the semiconductor wafer to function. Fixed abrasive pads include abrasive particles embedded within a polymer matrix. To operate a CMP system having a fixed abrasive pad, the fixed abrasive pad must first be conditioned. Traditionally, fixed abrasive pads are conditioned by polishing a patterned semiconductor wafer. The patterned semiconductor wafer conditions the fixed abrasive pad by using the topography features created by the etching and deposition processes on the semiconductor wafer to remove a portion of the polymer matrix, thus exposing the abrasive particles embedded within. By exposing abrasive particles within the polymer matrix, the fixed abrasive pad can begin to polish the semiconductor wafer. In order to continuously condition a fixed abrasive pad, patterned wafers with sufficient topography have to be continuously polished. The fresh, unconditioned fixed abrasive pad exhibits an unpredictable removal rate and needs to be conditioned prior to running product wafers. Typically, dummy patterned wafers are used to prepare the pad for product wafer polishing. These dummy wafers cost a considerable amount of money to manufacture, and the loading of these dummy wafers onto a CMP system takes up a considerable amount of time. Accordingly, further development of an apparatus and method for conditioning a chemical mechanical planarization process, and more specifically, for conditioning a fixed abrasive pad used in the chemical mechanical planarization of semiconductor wafers, is necessary in order to decrease the cost and time for conditioning a fixed abrasive pad.
According to a first aspect of the present invention, an apparatus for conditioning a fixed abrasive polishing pad used in chemical mechanical planarization of semiconductor wafers is provided. The apparatus includes a conditioning member formed from glass, at least one collimated hole structure located within the conditioning member, wherein the collimated hole structure forms a channel, and wherein each channel is arranged in a generally parallel orientation with respect to any other channel. In one embodiment, the conditioning member includes a material selected from the group consisting of borosilicate glass, soda lime glass, high-lead glass, silicon oxide, and quartz. In another embodiment, each channel within each collimated hole structure has a width of between about 3 microns and about 100 microns.
According to another aspect of the present invention, a method for conditioning a fixed abrasive polishing pad used in chemical mechanical planarization of semiconductor wafers is provided. The method includes providing at least one conditioning member formed with at least one capillary tube array, wherein the capillary tube array forms multiple channels within the conditioning member, pressing the conditioning member against the fixed abrasive polishing pad, and rotating or otherwise moving the fixed abrasive polishing pad. In one embodiment, the method further comprises rotating the conditioning member to simulate the polishing of at least one semiconductor wafer. In one embodiment, the fixed abrasive polishing pad comprises abrasive particles embedded within a polymer matrix.